Liquid crystal display apparatus and method for grounding liquid crystal display apparatus

ABSTRACT

Disclosed is a liquid crystal display apparatus, including: a liquid crystal display panel; a polarizing plate which is processed to be conductive and is attached to a surface of the liquid crystal display panel; and a conductive frame, wherein the polarizing plate includes a projecting area which projects outward from the edge of the liquid crystal display panel, and wherein the conductive frame presses the projecting area of the polarizing plate in order to ground the polarizing plate. A method for grounding a liquid crystal display apparatus is also disclosed.

The present Application is a Divisional Application of U.S. patentapplication Ser. No. 11/902,912, filed on Sep. 26, 2007.

RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2006-262221, filed on Sep. 27, 2006, thedisclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display apparatus anda method for grounding the liquid crystal display apparatus.

2. Description of the Related Art

Generally, a liquid crystal display apparatus includes a liquid crystaldisplay panel, a backlight unit and a chassis (case). The backlight unitis arranged at a back face of the liquid crystal display panel. Theliquid crystal display apparatus includes a structure in which theliquid crystal display panel integrated with the backlight unit isinstalled in a metallic frame (i.e. the chassis).

The liquid crystal display panel includes a liquid crystal drivingcircuit substrate, an opposite substrate, a sealing member and a liquidcrystal material. The liquid crystal driving circuit substrate and theopposite substrate are oppositely arranged with a gap therebetween whichis formed by the sealing member. The liquid crystal material is disposedin the gap to form the liquid crystal display panel. The liquid crystaldriving circuit substrate includes a liquid crystal driving circuit on asurface thereof (the inner surface) which contacts the liquid crystalmaterial.

Some opposite substrates of the liquid crystal display panels do notinclude a conductor on surfaces thereof. That is, such oppositesubstrate is not connected electrically anywhere and consequently, is inan electrically floating state. For example, a liquid crystal displayapparatus of a normally black mode type according to IPS (In-PlaneSwitching) method includes the opposite substrate above mentioned.

A polarizing plate including a conductor on a surface thereof thereon isattached to a surface of the opposite substrate in the electricallyfloating state in order to discharge an electric charge (i.e. staticelectricity) on the opposite substrate. The opposite substrate isgrounded (GND) when the conductor mounted on the surface of thepolarizing plate contacts the metallic frame.

In such liquid crystal display panel, the polarizing plate at theopposite substrate side is smaller than an external shape of the liquidcrystal display panel. Therefore, the conductor for grounding is pressedphysically by the metallic frame against the polarizing plate arrangedon a surface of the liquid crystal display panel. As a result, a stressis applied to the liquid crystal display panel, and consequently, thestress causes an uneven image on a screen.

Methods for grounding from the surface of the polarizing plate at theopposite substrate side according to a related art will be described inFIG. 3 to FIG. 7. Japanese Patent Application Laid-Open No. 2004-355035(Japanese Patent Application No. 2004-270865) discloses a liquid crystaldisplay apparatus having a structure for grounding the oppositesubstrate mentioned above. FIG. 3 is a cross sectional view showing thedisclosed liquid crystal display apparatus. FIG. 4 is a cross sectionalview showing a structure of the polarizing plate shown in FIG. 3. FIG. 5is a fragmentary cross sectional view showing details of the liquidcrystal display panel shown in FIG. 3.

The liquid crystal display apparatus shown in FIG. 3 includes a liquidcrystal material 11, an upper polarizing plate 13 b, a conductor 16 a, ametallic frame 180, a lower polarizing plate 15 a, a backlight unit 19and a printed wiring board 21. The conductor 16 a includes, for example,a conductive rubber and forms electrical connection between the upperpolarizing plate 13 b and the metallic frame 180.

As shown in FIG. 4, the upper polarizing plate 13 b includes athree-layered structure having an optical polarizing layer 131, aconductive layer 132 and an antireflection layer 133. Both-sidedadhesive tapes formed on both sides of the conductor 16 a bond the upperpolarizing plate 13 b and the conductor 16 a and bond the metallic frame180 and the conductor 16 a. The conductive layer 132 is, for example, anITO (Indium Tin Oxide) film formed with the sputtering method. A filmmade of SiO2 is formed as the antireflection layer 133 on the surface ofthe conductive layer 132 for protection thereof.

An opposite substrate 12 and an opposite substrate side polarizing plate13 a shown in FIG. 5 correspond to the upper polarizing plate 13 b shownin FIG. 3. A liquid crystal driving circuit substrate 14 and a liquidcrystal driving circuit side polarizing plate 15 b shown in FIG. 5correspond to the lower polarizing plate 15 a shown in FIG. 3. Theliquid crystal display panel has a structure that the liquid crystaldriving circuit substrate 14 and the opposite substrate 12 areoppositely arranged with a predetermined gap and are sealed by a sealingmember 17. The liquid crystal material 11 is disposed in the gaptherebetween. The polarizing plate 13 a at the opposite substrate sideis adhered to a front surface (i.e. a display surface side) of theliquid crystal display panel. The polarizing plate 15 a at the liquidcrystal driving circuit side is adhered to a rear surface of the liquidcrystal display panel.

According to the structure shown in FIG. 5, when the metallic frame 180presses the conductor 16 a against the polarizing plate 13 a at theopposite substrate side arranged on the surface of the liquid crystaldisplay panel, an electrical grounding is secured. However, stress isapplied to the liquid crystal display panel, and consequently, an unevenimage on a screen due to the stress is generated. If the stress is madeso small that the uneven images do not occur, the electric resistancebetween the polarizing plate 13 a at the surface of the oppositesubstrate side and the metallic frame 180 via the conductor 16 a becomeslarge. As a result, the electric charge can not be dischargedsufficiently.

FIG. 6 is a fragmentary cross sectional view showing other liquidcrystal display apparatus disclosed in Japanese Patent ApplicationLaid-Open No. 2004-355035. According to the disclosed structure, themetallic frame 180 and the polarizing plate 13 a at the oppositesubstrate side are connected electrically each other through aconductive tape 20, instead of the conductor 16 a. In this case, sincethe conductive tape 20 is adhered to the surface of the polarizing plate13 a at the opposite substrate side, the electric charge can bedischarged to the metallic frame 180 without the stress originated withthe metallic frame 180 which is applied to the surface of the liquidcrystal display panel. However, according to the structure, when theliquid crystal display panel and the backlight unit 19 are installed inthe metallic frame 180, it becomes necessary to perform a step foradhering the conductive tape 20 which is an extra process. As a result,production cost of the liquid crystal display apparatus increases due tothe additive step in the assembly process of the apparatus.

FIG. 7 is a fragmentary cross sectional view showing further otherliquid crystal display apparatus disclosed in Japanese PatentApplication Laid-Open No. 2004-355035. According to the apparatus, aconductive tape 20 a is used. Here, the conductive tape 20 a is adheredto a metal part 22 of the backlight unit 19 instead of the metallicframe 180. Accordingly, the apparatus includes the same difficulty asthe apparatus shown in FIG. 6.

SUMMARY OF THE INVENTION

The present invention has been proposed in view of the above mentionedcircumstances. The object of the present invention is to provide aliquid crystal display apparatus in which a stress is not applied to aliquid crystal display panel and an uneven image does not occur, even ifa strong contact is made on a surface of a polarizing plate forconnection to the ground, and to provide a method for grounding theliquid crystal display apparatus.

The present invention provides a liquid crystal display apparatus,including: a liquid crystal display panel; a polarizing plate which isprocessed to be conductive and is attached to a surface of the liquidcrystal display panel; and a conductive frame, wherein the polarizingplate includes a projecting area which projects outward from the edge ofthe liquid crystal display panel, and wherein the conductive framepresses the projecting area of the polarizing plate in order to groundthe polarizing plate.

Further, the present invention provides a method for grounding a liquidcrystal display apparatus including a liquid crystal display panel, apolarizing plate which is processed to be conductive, and a conductiveframe, the method including: attaching the polarizing plate to a surfaceof the liquid crystal display panel so that the polarizing plateincludes a projecting area which projects outward from the edge of theliquid crystal display panel; and grounding the polarizing plate throughthe conductive frame which presses a surface of the projecting area ofthe polarizing plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary features and advantages of the present invention will becomeapparent from the following detailed description when taken with theaccompanying drawings in which:

FIG. 1 is a fragmentary cross sectional view showing a first exemplaryembodiment of the present invention.

FIG. 2 is a fragmentary cross sectional view showing a second exemplaryembodiment of the present invention.

FIG. 3 is a cross sectional view showing a related art of a liquidcrystal display apparatus.

FIG. 4 is a cross sectional view showing a structure of the polarizingplate shown in FIG. 3.

FIG. 5 is a fragmentary cross sectional view showing details of theliquid crystal display panel shown in FIG. 3.

FIG. 6 is a fragmentary cross sectional view showing other related artof the liquid crystal display apparatus.

FIG. 7 is a fragmentary cross sectional view showing further otherrelated art of the liquid crystal display apparatus.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention will now be described indetail in accordance with the accompanying drawings.

First Exemplary Embodiment

FIG. 1 is a cross sectional view of a part of a liquid crystal displayapparatus according to a first exemplary embodiment of the presentinvention. As shown in FIG. 1, the liquid crystal display apparatusaccording to the embodiment includes a liquid crystal material 11, anopposite substrate 12, a polarizing plate 13 at an opposite substrateside, a liquid crystal driving circuit substrate 14, a polarizing plate15 at a liquid crystal driving circuit side, a conductor 16, a sealingmember 17, a metallic frame 18 and a backlight unit 19.

The liquid crystal driving circuit substrate 14 and the oppositesubstrate 12 are oppositely disposed each other by the sealing member 17so that a gap is formed therebetween. The liquid crystal material 11 isput into the gap to form the liquid crystal display panel. A liquidcrystal driving circuit is mounted on an inner surface of the liquidcrystal driving circuit substrate 14, which contacts the liquid crystalmaterial 11. The opposite substrate 12 does not include a conductivelayer over a surface thereof and then is electrically floated. Since theopposite substrate 12 tends to be influenced by an electric charge (i.e.static electricity), the polarizing plate 13 at the opposite substrateside whose surface includes a conductive layer is attached or adhered toan outer surface of the opposite substrate 12.

In the exemplary embodiment, the polarizing plate 13 at the oppositesubstrate side is larger than an external shape of the liquid crystaldisplay panel (that is, the size of the external shape of the oppositesubstrate 12 and the liquid crystal driving circuit substrate 14). Thatis, when the polarizing plate 13 at the opposite substrate side isattached or adhered to a surface of the opposite substrate 12, a part ofthe polarizing plate 13 projects outward from the edge of the liquidcrystal display panel (i.e., a projecting area). Moreover, the surfaceof the projecting area of the polarizing plate 13, which is processed tobe conductive, is electrically connected to the metallic frame 18 viathe conductor 16. As a result, the opposite substrate 12 is grounded(GND) via the metallic frame 18 and an electric charge thereon aredischarged. Further, the polarizing plate 15 at the liquid crystaldriving circuit side is attached to an outer surface of the liquidcrystal driving circuit substrate 14.

The exemplary embodiment includes following features compared with therelated art shown in FIG. 3 to FIG. 7.

(1) the polarizing plate 13 at the opposite substrate side includes apart or area which projects outward from the edge of the external shapeof the liquid crystal display panel.

(2) the electric connection to the ground is secured through theprojecting area or part of the polarizing plate 13 which is pressedphysically via the conductor 16 by the metallic frame 18.

There are many methods to connect electrically to the surface of thepolarizing plate 13 at the opposite substrate side for grounding.However, when the conductor 16 is pressed to the polarizing plate 13,the stress due to the press is applied to the opposite substrate 12which is one of elements of the display panel. Consequently, unevenimage is generated on a screen. In particular, in the liquid crystaldisplay apparatus of a normally black mode type according to IPS(In-Plane Switching) method, a white spot as unevenness occurs on ablack screen. The unevenness on a screen may be generated by a smallstress. If the stress to the polarizing plate 13 at the oppositesubstrate side is reduced in order to avoid generation of the unevennesson a screen, the electric connection to the ground becomes insufficient.

According to the exemplary embodiment, a part of the polarizing plate 13at the opposite substrate side projects outward from the edge of theliquid crystal display panel. Moreover, the conductor 16 for groundingpresses the projecting area of the polarizing plate 13 which is locatedon an upper part of the backlight unit 19. Accordingly, although thestress is applied to the projecting area of the polarizing plate 13 atthe opposite substrate side, the stress is not applied to the screen(i.e. the opposite substrate 12) of the liquid crystal display panel.Accordingly, it is possible to display an excellent image without theunevenness, since the liquid crystal display panel is free from stressand the electric connection for grounding can be secured sufficiently.

Next, a method for manufacturing the liquid crystal display apparatusshown in FIG. 1 will be described. First, the liquid crystal drivingcircuit substrate 14 and the opposite substrate 12 are oppositelydisposed, via the sealing member 17, with a predetermined gaptherebetween. The gap is filled with the liquid crystal material 11 andis sealed by the sealing member 17 to form the liquid crystal displaypanel. Next, the polarizing plate 13 is attached to an outer surface ofthe opposite substrate 12 in the display panel. Also, the polarizingplate 15 is attached to an outer surface of the liquid crystal drivingcircuit substrate 14. An outer surface of the polarizing plate 13, whichdoes not contact the opposite substrate 12, is processed to beconductive so that an electric charge on the display panel can bedischarged. The process for forming conductivity may include a method ofvapor deposition of conductor, such as transparent metal, on thepolarizing plate 13, and a method of applying transparent resinincluding metallic fillers to the polarizing plate 13.

When the liquid crystal display apparatus is assembled, the conductor 16is mounted on the metallic frame 18 so that the conductor 16 can connectthe conductive projecting area of the polarizing plate 13. Thepolarizing plate 13 and the metallic frame 18 are electrically connectedand fixed each other via the conductor 16, for example, with adouble-faced adhesive tape, an adhesive or the like, each of which iselectrically conductive. As a result, electric connection between thepolarizing plate 13 and the metallic frame 18 which is connected to theground (GND) can be secured. The metallic frame 18 can be made of metalsuch as stainless steel. The conductor 16 can be metallic spring,electrically conductive rubber or the like. Further, the metallic frame18 may be made of material other than metal. That is, a conductive framewhose conductivity can secure the electric connection to the ground maybe employed as the substitution of the metallic frame 18.

Second Exemplary Embodiment

Next, a second exemplary embodiment of the present invention will bedescribed with reference to drawings. FIG. 2 is a cross sectional viewof a part of a liquid crystal display apparatus according to the secondexemplary embodiment of the present invention. The conductor 16 shown inFIG. 1 is not used in FIG. 2. In FIG. 2, a metallic frame 18 a includesan elastic contact part 18 b which is formed to be convex toward theprojecting area of the polarizing plate 13 through processing themetallic frame 18 a. The contact part 18 b touches and presses theprojecting area of the polarizing plate 13 to make electric contacttherewith. The contact part 18 b of the metallic frame 18 a can beprocessed with various methods such as bending work and press work.

Electric connection between the metallic frame 18 a and the polarizingplate 13 can be formed by strong contact between the contact part 18 band the projecting area of the polarizing plate 13. Moreover, unevenimage on a screen due to stress applied to the liquid crystal displaypanel is not generated, because the stress is not applied to the panel.Further, the metallic frame 18 a according to the exemplary embodimentmay be made of a conductive frame other than metal. A number ofcomponents and cost thereof can be reduced in the second embodiment,compared with the first embodiment, since it is unnecessary to use theconductor 16 mounted on the metallic frame 18 a.

As described above, according to the exemplary embodiments of thepresent invention, the part of the polarizing plate which is adhered tothe surface of the liquid crystal display panel projects outward fromthe external shape of the display panel. The projecting area of thepolarizing plate 13 is pressed from the conductive frame to makeelectric contact for grounding. Therefore, uneven image on a screen isnot generated, since no stress is applied to the liquid crystal displaypanel even though the conductive frame strongly presses the polarizingplate to make electric contact for grounding.

The previous description of embodiments is provided to enable a personskilled in the art to make and use the present invention. Moreover,various modifications to these embodiments will be readily apparent tothose skilled in the art, and the generic principles and specificexamples defined herein may be applied to other embodiments without theuse of inventive faculty. Therefore, the present invention is notintended to be limited to the embodiments described herein but is to beaccorded the widest scope as defined by the limitations of the claimsand equivalents.

Further, it is noted that the inventor's intent is to retain allequivalents of the claimed invention even if the claims are amendedduring prosecution.

1. A liquid crystal display apparatus, comprising: a liquid crystaldisplay panel; a polarizing plate which is processed to be conductiveand is attached to a surface of the liquid crystal display panel; and aconductive frame, wherein the polarizing plate includes a projectingarea which projects outward from the edge of the liquid crystal displaypanel, and wherein the conductive frame presses the projecting area ofthe polarizing plate in order to ground the polarizing plate.
 2. Theliquid crystal display apparatus according to claim 1, wherein theconductive frame includes an elastic contact part, which touches thepolarizing plate in order to ground the polarizing plate.
 3. A methodfor grounding a liquid crystal display apparatus including a liquidcrystal display panel, a polarizing plate which is processed to beconductive, and a conductive frame, the method comprising: attaching thepolarizing plate to a surface of the liquid crystal display panel sothat the polarizing plate includes a projecting area which projectsoutward from the edge of the liquid crystal display panel; and groundingthe polarizing plate through the conductive frame which presses asurface of the projecting area of the polarizing plate.
 4. The methodfor grounding the liquid crystal display apparatus according to claim 3,wherein the conductive frame includes an elastic part, which touches thepolarizing plate in order to ground the polarizing plate.